Create E2E test for User membership mapping feature of Direct transfer

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Based on this conversation, There is a "Import User memberships" checkbox on the Import page which might need an E2E test. But I need to gather more information on this to continue.

Currently we have E2E API based test for group member and project member imports -https://gitlab.com/gitlab-org/gitlab/-/blob/master/qa/qa/specs/features/api/1_manage/migration/gitlab_migration_members_spec.rb